OXYGEN BEHAVIOR IN ND2-XCEXCUO4-DELTA OBSERVED BY RESISTIVITY MEASUREMENTS

We present in situ resistivity measurements of the high-temperature ph ase behavior associated with oxygen variation of the ceramic system Nd 2-xCexCuO4-delta (NCCO) when annealed in ambient air. We observed a re sistivity anomaly around 550 K in all deoxygenated samples prepared by rapid cooling into liquid N2, which is smaller for higher Ce content. We attribute this anomaly to oxygen in-diffusion, which is less with increasing x. The implications of these results on the role of the oxy gen vacancies to establish a metallic phase in NCCO are discussed.